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97S low battery Indicator with no display
03-01-2023, 02:29 AM (This post was last modified: 03-01-2023 02:31 AM by John Garza (3665).)
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John Garza (3665) Offline
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RE: 97S low battery Indicator with no display
CR5 and Q2 both test good. So maybe Q2 is over-driven. I looked at the signal on the base of Q2 and it looks to be a sloppy waveform at 550KHz. A reference known good HP-97 showed around 50KHz with a more squarish wave. Maybe Q3 or CR9 aren't keeping the oscillation in range? The service manual says it should be 20KHz, but my 97 is working fine at 50. So the 97S is oscillating much faster than it should be!

-J

   
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RE: 97S low battery Indicator with no display - John Garza (3665) - 03-01-2023 02:29 AM



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